Facebook on Thursday added video to its already popular Instagram mobile photo-sharing app, a feature that could counter the rapidly growing popularity of Twitter's video app Vine.

As with Vine, Video on Instagram gives its 130 million monthly users the ability to record and post ultra-short video clips directly from their mobile iOS and Android smartphones and tablets. But Instagram is giving users more than double the time - a maximum of 15 seconds, compared with six seconds for Vine.

And Video on Instagram also includes 13 filters, similar to the special effects that made its photo-sharing app popular, and built-in image stabilization software to reduce annoying "shaky hand" video.

Down the line, video could open a potential revenue stream for Facebook, which paid a premium price worth more than $700 million in cash and stock last year to buy Instagram, which had little discernable income.

But Instagram co-founder Kevin Systrom insisted the new video feature was not specifically designed to generate revenue, even though the 15-second videos can be more than enough time for a paid TV-style commercial.

"This is really driven by consumer demand and not by business need," Systrom said during a news conference at Facebook headquarters in Menlo Park. "I don't think we designed it with any advertising in mind. Right now, we're perfectly happy with how businesses are engaging on Instagram, which is organically."

Multimedia content

The release of Video on Instagram underscores the growing overall impact of online and mobile video, especially as companies like Facebook and Twitter court younger audiences well versed in sharing and viewing all types of multimedia content.

San Francisco's Twitter introduced Vine, which is specifically designed for short video, just 4 1/2 months ago. By June 3, it had more than 13 million registered users. And that was before Twitter released an Android version of Vine.

In just that short time, Vine's level of user engagement - a measure of replies, retweets and favorites - is already "staggeringly close" to that of Google's far more established YouTube, according to a report released this week by Socialbakers, a social media analytics firm.

"Twitter users increasingly appreciate this format, and brands who may have previously not considered Vine should sit up and take notice," said Socialbakers CEO Jan Rezab. "Not only are Vine videos evidently engaging, but they can be produced on a smaller budget."

Ad space

Analyst Brian Blau of research firm Gartner said he doesn't expect an immediate rush of commercial advertising on Instagram, but said: "I think over time you'll see advertisers come in."

It also may take time for marketers to figure out whether to use Vine or Video for Instagram "as their calling card," he said.

Facebook and Instagram may make that choice easier with the different tools they added to distinguish their app from Vine.

"They wanted to make it easy, and video is inherently not easy," Blau said. "What Facebook did is to keep it minimal, but give them (the users) enough tools to make compelling content."

Instagram's founders originally intended to add video, but that capability was set aside because mobile devices at the time only allowed the kind of desired "speed and simplicity" for sharing photos, Systrom said.

Instagram users have shared about 16 billion photos and posted more than 1 billion likes on the app, he said.

Time 'just right'

When asked why Instagram chose 15 seconds instead of anything longer or shorter, Systrom said the company tested several lengths and found 15 seconds was "that Goldilocks moment of 'it feels just right.' Not too long, in which case the video takes forever to download over a mobile network on the go; not too short, in that you're trying to record your kid and you don't get that special moment. That, plus the editing tools, gives us the right balance."

A Twitter spokeswoman said her company tested Vine videos of four to 10 seconds in length but found a maximum six seconds were ideal for production and viewing.

Systrom said the choice could be in the eye of the beholder.

"I think it's an artistic choice," he said. "Honestly, I don't that think one is better than the other. Depending on the length of time that you give users, you're going to get different content."